Myotonia congenita

Superficial anterior muscles

Superficial muscles are close to the surface of the skin. Muscles which lie closer to bone or internal organs are called deep muscles.

Also known as: Thomsen's disease and Becker's disease

Definition

Myotonia congenita is an inherited condition that affects muscle relaxation. It is congenital, meaning that it is present from birth.

Causes, incidence, and risk factors

Myotonia congenita is caused by a genetic change (mutation). It is passed down from either one or both parents to the children (inherited).

Myotonia congenita is caused by a problem in the part of the muscle cells that are needed for muscles to relax. Abnormal repeated electrical discharges occur in the muscles, causing a stiffness called myotonia.

Symptoms

The hallmark of this condition is the myotonia -- the inability of the muscle to quickly relax after contracting. For example, after a handshake, the person is only very slowly able to open and pull away his hand.

Early symptoms may include:

  • Difficulty in swallowing
  • Gagging
  • Stiff movements that improve when they are repeated
  • Shortness of breath or tightening of the chest at the beginning of exercise

Children with myotonia congenita often appear to be muscular and well-developed. The child may not have symptoms of myotonia congenita until age 2 or 3.

Signs and tests

The doctor may ask if there is a family history of myotonia congenita.

Tests include:

  • Genetic testing
  • Muscle biopsy
  • Test of the electrical activity in muscles (EMG)

Treatment

Treatment for symptoms includes:

  • Mexiletine
  • Phenytoin
  • Procainamide

Expectations (prognosis)

People with this condition can do well. Symptoms only occur when a movement is first started. After a few repetitions, the muscle relaxes and the movement becomes normal. Symptoms may improve later in life.

Complications

  • Aspiration pneumonia caused by swallowing difficulties
  • Frequent choking, gagging, or difficulty swallowing in an infant
  • Abdominal muscle weakness
  • Chronic joint problems

Calling your health care provider

Call your health care provider if your child has symptoms of myotonia congenita.

Prevention

Genetic counseling may be of interest to couples who want to have children and have a family history of myotonia congenita.

References

Barohn RJ. Muscle diseases. Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 447.

Bernard G, Shevell MI. Channelopathies: a review. Pediatr Neurol. 2008 Feb;38(2):73-85.

See also:

  • Special Topic

    Autosomal recessive

    Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families. An autosomal recessive disorder means two copies of an abnormal must be present in order for the disease or trait to develop.

  • Disease

    Aspiration pneumonia

    Pneumococci organism

    Aspiration pneumonia is inflammation of the lungs and airways to the lungs (bronchial tubes) from breathing in foreign material.

  • Special Topic

    Autosomal dominant

    Autosomal dominant genes

    Autosomal dominant is one of several ways that a trait or disorder can be passed down through families. If a disease is autosomal dominant, it means you only need to get the abnormal from one parent in order for you to inherit the disease. One of the parents may often have the disease.

Review date:
March 21, 2010
Reviewed by:
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Luc Jasmin, MD, PhD, Department of Neurosurgery at Cedars-Sinai Medical Center, Los Angeles, and Department of Anatomy at UCSF, San Francisco, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
Copyright Information A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2008 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.